Pressure assisted tension roller leveler

ABSTRACT

A PRESSURE ASSISTED TENSION ROLLER LEVELER EMBODYING MEANS FOR APPLYING PRESSURE NORMAL TO THE STIP DURING PASSAGE BETWEEN THE WORK ROLL AND THE FLEXURE ROLLS AND FOR PROVIDING FLEXIBILITY CROSSWISE BETWEEN THE WORK ROLL AND FLEXURE ROLLS.

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Sept. 20, 1971 N. POLAKOWSKI 3,605,470

PRESSURE ASSISTED TENSION ROLLER LEVELER Filed on. 5, 1969 Sheets-Sheet s 3 Sheets-Shasta U 1.": nl. n m

Q S p 20, 1971 N. H. POLAKOWSKI PRESSURE ASSISTED TENSION momma mvmwa] f 7 Filed Oct. :5, 1969 United States Patent 3,605,470 PRESSURE ASSISTED TENSION ROLLER LEVELER Natalis H. Polakowski, 226 Laurel Ave., Wilmette, Ill. 60091 Continuation-impart of application Ser. No. 793,981, Jan. 27, 1969. This application Oct. 3, 1969, Ser. No. 863,657

Int. Cl. B21d 1/02 US. Cl. 72-163 9 Claims ABSTRACT OF THE DISCLOSURE A pressure assisted tension roller leveler embodying means for applying pressure normal to the stip during passage between the work roll and the flexure rolls and for providing flexibility crosswise between the Work roll and flexure rolls.

This is a continuation-in-part of my copending application Ser. No. 793,981, filed Jan. 27, 1969, now abandoned and entitled Pressure Assisted Tension Roller Leveler.

This invention relates to the art of leveling or flattening metal strip and to apparatus for effecting same.

Tension roller leveling of metal strip represents an accepted procedure for flattening of malshaped metal strip afllicted with local waves, puckers and corrugations. These various distortions are a function of length differences between adjacent, parallel portions of the strip, when measured in the lengthwise direction. The larger the percentage difference, the more pronounced are the deviations from ideal flatness. To restore the latter, the short portions should be actually stretched to eliminate the aforesaid percent differences, for equalization of the short and long elements.

To accomplish the aforesaid objective, a longitudinal pulling load would be applied sufficient to exceed the yield stress of the material. In many instances this would represent a large value whereby this procedure becomes unsuitable for heavily cold rolled strip, due to the low residual ductility remaining in the metal. The required pull can be reduced by making use of the combination of tension and bending, with the strip being bent by wrapping about a portion of the periphery of one or a sequence of hard flexing or work rollers. The sequence is such that the strip is flexed in alternate directions on adjacent rollers which is a practice familiar to those skilled in the art of roller leveling.

The effectiveness of the bending action in reducing the required bulk tension to effect flattening is a function of the ratio of strip thickness (t) to work roll diameter (d). The larger this ratio, the less the tension required to achieve a predetermined in-process extension. The several parameters are related in the following approximate equation: e=Tt(S d) in which 2 is the engineering strain (percent extension=100e), T is the mean tension in p.s.i. applied to the strip, t is strip thickness, S is the yield stress of the metal and d is roll diameter. From actual experience, it has been determined that d should normally not exceed 100t in order to keep T at a reasonable and safe level. Ratios as low as d :t=35-50 are desirable with hard rolled metals, such as double reduced tin plate or cold rolled 300-type stainless steels.

The described ratio requirements impose a number of problems. For example, with metal strip as thin as .006 inch, it would be desirable to make use of a work roll having a diameter of 0.25 to 0.375 inch. To obtain the desirable through-put speed of 500 feet per minute, a inch roll would have to rotate at a speed of 7500 rpm. Further, since some axial thrust usually arises during tension leveling, with such thrusts generally increasing with 3,605,470 Patented Sept. 20, 1971 increase in strip width, such thin. work rolls may present problems from the standpoint of buckling and stability.

In addition, their physical size makes them impractical for use at sufliciently high'speeds, such as are called for by economic considerations in processing of low unit cost products, such as tin plate or light gauge can stock. On the other hand, increase in work roll diameted to 0.75 to 1 inch increases the tension requirements about two to three fold whereby operation becomes subject to possible strip breakage.

I have found that one possibility for alleviation of the involved situation is to apply a pressure C normal to the surface of the strip to assist the tension whereby the latter can be kept at safe levels. The metal will then deform plastically at a tension T reduced approximately to owing to the compressive stress or pressure acting on the strip. This principle has been employed in cold strip rolling under tension. To obtain a given reduction or extension, one can increase roll pressure and reduce tension and vice versa. Actually, with respect to a roller leveler, the added pressure normal to the strip will replace a portion of the bending stress developed by wrapping the strip about the portion of the work roll. This will, in turn, permit the use of a large work roll for flattening.

A conventional leveler designed to embody the above concepts would represent a rolling mill inasmuch as the distance between intermeshing rollers would be somewhat less than the thickness of the material. Moreover, because of the rigidity of the structure, the thicker portions of the strip would be reduced percentagewise more than the adjacent thinner portions. This would tend to create waviness and poor shape rather than to alleviate it.

It is an object of this invention to provide a pressure assisted tension roller leveler which is effective to improve flatness in a simple and efficient manner and it is a related object to provide a machine for effecting same.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, embodiments of this invention are shown in the accompanying drawings, in which FIG. 1 is a schematic sectional view of one embodiment of the roller assembly for carrying out the practice of this invention;

FIG. 2 is a schematic sectional elevational view of another modification of roller assembly;

FIG. 3 is a schematic sectional elevational view showing still further modifications of rollers and supports for carrying out the practice of this invention;

FIG. 4 is a schematic sectional view of a base support for flexing rollers embodying the features of this invention; and

FIG. 5 is a schematic elevational view of a roller assembly embodying the features of this invention.

In accordance with the practice of this invention, difiiculties of the type described are eliminated by incorporating into the design of the leveler a large degree of roller flexibility to enable the material to be worked between rollers which can easily deflect to accommodate variations in transverse thickness in the strip. Such flexibility prevents localized spots of greater thickness from being forcibly ironed out with consequent generation of loose pockets. These features can be achieved in a number of ways which may be employed singly or in various combinations, as will hereinafter be described.

The segment of the roller leveler illustrated in FIG. 1 shows a work roll 1 of small diameter supported by a backing roll 2 of much larger diameter with the backing roll 2 cradled on two parallel rows of roller bearings 3 mounted on axel 3 fixed for support on ribs 8.

a of the work roll 1 to flex strip 4 about a portion of the work roll as it passes between the work roll 1 and the deflector rolls 5 and 6. The deflector rolls are cradled in three parallel rows of bearings 7 mounted on axles 7 fixed to a frame.

Pressure assistance is provided to the work roll 1 by means of a backup beam 9 on which the ribs 8 are supported with the beam actuated by hydraulic means such as a fluid cylinder and piston arrangement 10 for displacement of the lower roll assembly to apply the desired compressive forces at the point of contact between the work roll 1 and the strip.

If the backup beam 9 is very rigid by reason of its large section modulus, the lower roll assembly supported by it can be regarded as rigid or non-flexible for all practical purposes. In such event, the desired flexibility across the machine is provided by making the deflector rolls 5 and 6 hollow, as illustrated in FIG. 1.

Instead of providing the desired flexibility by hollow deflector rolls, the desired flexibility can be obtained by the construction wherein the backup roll in the hollow roll, as illustrated in the succeeding flexing station in FIG. 1 by the backup roll 12. In this succeeding station the hollo'w backup roll 12 is cradled between bearings 13 while the deflector rolls 14 and 15 for the work roll 11 are cradled on bearings 16 mounted on ribs 16 with the lower cluster of deflector rolls being supported on backup beam 17 mounted for movement in the direction toward and away from the work roll by the pressure fluid operated piston and cylinder assembly or hydraulic jacks 18.

Instead of relying on hollow backup and/or deflector rolls to provide the desired lateral flexibility in the pressure assisted system, or in combination therewith, the desired lateral flexibility can be achieved by construction of the backup beams 9 or 17 to be relatively light and flexible and supporting the beams at numerous, usually equidistant points across the Width, with jacks, such as illustrated by the numerals 10 and 18. The jacks can be separately actuated but it is preferred hydraulically to interconnect the jacks to provide a relatively uniform linear preload on the work roll and strip and a fixed pressure can be provided which is unaffected by variations in strip thickness thereby to avoid rolling as distinguished from a leveling action. Instead of hydraulic jacks, use can be made of mechanical jacks, such as screw or rack operated jacks, but only when transverse flexibility is provided by low-rigidity rolls such as 5, 6, and 12 in FIG. 1.

The complete leveler may consist of one or more stations of the type described followed preferably by a more conventional finish flattening stage where pressure assistance normal to the strip is not employed. This finishing portion which makes use of the flexing roll serves primarily to eliminate coil set and residual stresses from the metal.

FIG. 2 illustrates an alternative arrangement for pressure assisted roll leveling in accordance with the practice of this invention. In this modification, the work roll 19 is cradled between four rolls of larger dimension including deflector rolls 20 and a pair of backup rolls 20 The required flexibility can be provided by making the backup rolls 20 hollow and/or preferably by making the deflector rolls 20 hollow, as illustrated in the drawing. The strip 21 is passed between the work roll 19 and deflector rolls 20 with the other details of the roll assemblies being the same as in the assembly previously described.

FIG. 3 resembles a standard roller leveler except that work rolls 23 cradled in bearings and deflector rolls 24 cradled in bearings 25 are in positive contact through the strip 22. Jacks 26 of the construction previously described are mounted at least at the opposite ends of the backup beam 27 if the beam 27 is a stiff beam. If the beam is a flexible beam, then the jacks are provided at closely spaced intervals across the width of the beam. Extra flexibility is provided by the hollow work rolls 23. Rolls 24 can be either solid or hollow.

FIG. 4 shows an arrangement for maximizing flexibility in which the backup beam is relatively flexible and has a number of ribs 29 which mount to continuous or sectional axles on which the bearings 31 in FIG. 4 or 16 and 13 in FIG. 1 or 25 in FIG. 3 are mounted for free rotational movement. Thus each segment, in a sectionalized azle or rib, is individually yieldingly urged with predetermined force for pressure assistance of the flex roll in flattening with the aid of a series of hydraulic jacks 32.

For the remainder of the assembly for a complete flattener including the payout and windup rolls, the bridles and the like to provide longitudinal tension to the strip as it is drawn through the machine for the combination of pressure assisted tension leveling, reference can be made to my previously issued Pat. No. 3,344,637.

FIG. 5 illustrates an arrangement similar to that in FIG. 1 but modified so as to secure a tangential, free from flexure, entry of strip 33 into the nip of rolls 34 and 35. Such straight entry is particularly desirable in processing materials prone to form Luders lines or leveler breaks, such as annealed low carbon steel or hot-dip galvanized steel strip. The Luders lines form ordinarily upon bending the entering strip around a portion of the periphery of roll 35 and before the radial pressure is applied to it by hydraulic cylinders 38 via backing rolls 37. The details of the complete backup structure may follow those in FIG. 1 and need not be repeated. Likewise, rolls 35 and 36 can be hollow for reasons already explained. It will be recognized, of course, that to comply with the principle expressed in FIG. 5, the first leveler station in FIG. 1 must be inclined under a suitable angle.

It will be apparent from the foregoing that I have provided a new, simple and more eflicient means for roller leveling of metal strip.

It will be understood that changes may be made in the details of construction and operation without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

1. A pressure assisted tension roller leveler comprising a small diameter work roll, a pair of larger diameter flexure rollers mounted for rotational movement about axes parallel with the axis of the work roll with the peripheral surfaces of the flexure rollers spaced one from the other by an amount less than the diameter of the work roll while cradling the work roll therebetween for flexure of metal strip over a portion of the periphery of the work roll during pasage of the metal strip under tension between the work and flexure rolls, one set of bearing rolls cradling the flexure rolls to support the flexure rolls for rotational movement, backup rolls engaging the work roll on the side opposite the strip, another set of bearing rolls cradling the backup rolls to support the backup rolls for rotational movement, one frame member mounting the one set of bearing rolls and another frame member mounting the other set of bearing rolls, pressure generating means operatively engaging at least one of said frame members for applying pressure between said Work and flexure rolls normal to the strip passed therebetween, and means for inducing transverse flexibility in at least one of the rolls comprising the work roll and flexure rolls substantially to conform with transverse variations of the strip passing therebetween.

2. A pressure assisted tension roller leveler as claimed in claim 1 in which the flexure rolls are in the form of hollow tubular members to provide the means for the transverse flexibility.

3. A pressure assisted tension roller leveler as claimed in claim .1 in which the backup roll is in the form of a hollow tubular member to provide the transverse flexibility.

in claim 1 in which both the backup roll and the flexure rolls are in the form of hollow tubular members to provide the means for the transverse flexibility.

5. A pressure assisted tension roller leveler as claimed in claim 1 in which at least one of the sets of bearing rolls is subdivided crosswise into separate segments and in which the means for inducing transverse flexibility comprises means operatively engaging the separate segments for the transmission of pressure therethrough to the work and fiexure rolls. 7

6. A pressure assisted tension roller leveler as claimed in claim 5 in which the means operatively engaging the separate segments comprises fluid pressure means interconnected for transmission of uniform pressure to the separate segments.

7. A pressure assisted tension roller le veler as claimed in claim 1 in which at least one of the rolls including the backup roll and the flexure rolls is supported on continuous axles of low rigidity as the means for providing transverse flexibility.

5 a t. A pronto natal tonon 101101'10Y0l0l't15 claimed 6. A plenum Elfifililtfl lcnslon roller lcvclcr as iltlllltfl in claim 1 which includes means introducing the strip for engagement between the work roll and flexure roll without previous bending of the strip over one of said rolls.

9. A pressure assisted tension roller leveler as claimed in claim 1 in which the strip is introduced between the work roll and flexure roll in a direction tangential to said rolls at the point of engagement between the work and flexure rolls.

References Cited UNITED STATES PATENTS 3,260,093 7/ 1-966 Polakowski 72163 3,394,574 7/1968 Franek et a1. 7-2164X 3,513,677 5/1970 Polakowski 72163 MILTON S. MEHR, Primary Examiner US. Cl. X.R. 

